pololu 36v4

[enjoylife1024]

I am wondering how I would add the spi to the grbl so that it programs the driver chip at every power up. I am a very new to the whole programming stuff. I can modify the code to get the axis I need. And have grbl 5x working correctly now. I am using very large drives right now and the pololu is smaller foot print to get away from the large boxes I am using now. I just need to get the spi program to run on power up every time.

[fra589]

Hi @enjoylife1024,

Adding SPI communication protocol to grbl-Mega-5X is not impossible, but pretty complicated.
In fact, for performance reason, grbl is written in pure C language, not C++ and don't use any Arduino code. So, you will can't use any existent SPI C++ library, and you will have to write the SPI code by yourself.
Then, if you are able to do it, to run SPI communication when initializing grbl, you can do it from the main() function in the main.c file.

@++;
Gauthier.

[enjoylife1024]

Thank you so much for the response. I am also having an issue with the limit switches. I am not able to get them to turn on. I have put this in the discussion with the code I uploaded to the arduino. I have all of the code attached to the discussion. I would like to tell you thank you for writing this. I am doing prototype builds of cnc's right now and this is by far the best solution for the arduino as controller I have found. Very is to follow even though I have never messed with arduinos before. I only know how to pretty much get the code onto the arduino. But the way you wrote this code it is very easy to understand with absolutely no knowledge of coding. Hope to hear from you soon.

…

________________________________ From: Gauthier Brière ***@***.***> Sent: Saturday, May 17, 2025 3:30 AM To: fra589/cn5X ***@***.***> Cc: Roger Pelletier ***@***.***>; Mention ***@***.***> Subject: Re: [fra589/cn5X] pololu 36v4 (Discussion #48) Hi @enjoylife1024<https://github.com/enjoylife1024>, Adding SPI communication protocol to grbl-Mega-5X is not impossible, but pretty complicated. In fact, for performance reason, grbl is written in pure C language, not C++ and don't use any Arduino code. So, you will can't use any existent SPI C++ library, and you will have to write the SPI code by yourself. Then, if you are able to do it, to run SPI communication when initializing grbl, you can do it from the main() function in the main.c file. @++; Gauthier. — Reply to this email directly, view it on GitHub<#48 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/BDXYP7T5PVG62ZVDOAAQ7UT263QR7AVCNFSM6AAAAAB5JFYYTCVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGMJXG42TGOA>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[enjoylife1024]

Just to be clear in case we are not in the same page. The Pololu driver requires the settings to be written to the board at every power cycle, after that is complete, there is no need for any further SPI communication. I do not need to command movements using SPI at all, the driver just needs to be initialized once then it listens to the Step and Dir Pins. Below I will write the code that is needed just to get it into this initialized state. So the idea would be that GRBL would just do that at the beginning of boot up and then seize the SPI connection. Let me know if everything you previously stated still applies. Thank you.

#include <SPI.h>

#include <HighPowerStepperDriver.h>

const uint8_t CSPin = 49;

//This pin must cycle high and low. Pins 50 and above are staying high for some reason.****

// This period is the length of the delay between steps, which controls the

// stepper motor's speed. You can increase the delay to make the stepper motor

// go slower. If you decrease the delay, the stepper motor will go faster, but

// there is a limit to how fast it can go before it starts missing steps.

const uint16_t StepPeriodUs = 2000;

HighPowerStepperDriver sd;

SPI.begin();

sd.setChipSelectPin(CSPin);

// Give the driver some time to power up.

delay(1);

// Reset the driver to its default settings and clear latched status

// conditions.

sd.resetSettings();

sd.clearStatus();

// Select auto mixed decay. TI's DRV8711 documentation recommends this mode

// for most applications, and we find that it usually works well.

sd.setDecayMode(HPSDDecayMode::AutoMixed);

// Set the current limit. You should change the number here to an appropriate

// value for your particular system. If you are using a 36v8 board, call

// setCurrentMilliamps36v8 instead.

sd.setCurrentMilliamps36v4(4000);

// Set the number of microsteps that correspond to one full step.

sd.setStepMode(HPSDStepMode::MicroStep4);

// Enable the motor outputs.

sd.enableDriver();

[fra589]

Hi @enjoylife1024,

SPI and HighPowerStepperDriver libraries are Arduino C++ libraries.
As I said, grbl-Mega-5X is standard C code, not C++ and it don't use the Arduino system.
The provided Arduino sketch is provided only for calling the AVR compiler. This is to make building binaries easier for those who are not programmers. Personally, I never use the Arduino system to compile grbl-Mega-5X, I work under Linux and create my binaries with make/avrgcc.
Using the Arduino libraries SPI and HighPowerStepperDriver will call the Arduino C++ system inside the grbl's code and will break the whole code.
I'm sorry for you, but if you want to make your stepper initialisation inside grbl-Mega-5X, you will need to write the init code by yourself in pure C code and call it in the main() function.

Using the drv8711 datasheet: https://www.ti.com/lit/gpn/drv8711 and this example: https://github.com/cnc-board/motor_driver/blob/master/drv8711.c, this should be possible.

@++;
Gauthier.

[enjoylife1024]

Thank you sir! You are the man.